Active targeting and delivery to pathophysiological organs of interest is of paramount importance to increase specific accumulation of therapeutic drugs or imaging agents while avoiding systemic side effects. We recently developed a family of new peptide ligands of the human and rodent LDL receptor (LDLR), an attractive cell-surface receptor with high uptake activity and local enrichment in several normal or pathological tissues (Malcor et al., J. Med. Chem. 2012, 55 (5), 2227). Initial chemical optimization of the 15-mer, all natural amino acid compound 1/VH411 (DSGL[CMPRLRGC]DPR) and structure-activity relationship (SAR) investigation led to the cyclic 8 amino acid analogue compound 22/VH445 ([cMPRLRGC]) which specifically binds hLDLR with a K of 76 nM and has an in vitro blood half-life of ∼3 h. Further introduction of non-natural amino acids led to the identification of compound 60/VH4106 ([(d)-"Pen"M"Thz"RLRGC]), which showed the highest K value of 9 nM. However, this latter analogue displayed the lowest in vitro blood half-life (∼1.9 h). In the present study, we designed a new set of peptide analogues, namely, VH4127 to VH4131, with further improved biological properties. Detailed analysis of the hLDLR-binding kinetics of previous and new analogues showed that the latter all displayed very high on-rates, in the 10 sM range, and off-rates varying from the low 10 s to the 10 s range. Furthermore, all these new analogues showed increased blood half-lives in vitro, reaching ∼7 and 10 h for VH4129 and VH4131, respectively. Interestingly, we demonstrate in cell-based assays using both VH445 and the most balanced optimized analogue VH4127 ([cM"Thz"RLRG"Pen"]), showing a K of 18 nM and a blood half-life of ∼4.3 h, that its higher on-rate correlated with a significant increase in both the extent of cell-surface binding to hLDLR and the endocytosis potential. Finally, intravenous injection of tritium-radiolabeled H-VH4127 in wild-type or ldlr -/- mice confirmed their active LDLR targeting in vivo. Overall, this study extends our previous work toward a diversified portfolio of LDLR-targeted peptide vectors with validated LDLR-targeting potential in vivo.

Insufficient membrane penetration of drugs, in particular biotherapeutics and/or low target specificity remain a major drawback in their efficacy. We propose here the rational characterization and optimization of peptides to be developed as vectors that target cells expressing specific receptors involved in endocytosis or transcytosis. Among receptors involved in receptor-mediated transport is the LDL receptor. Screening complex phage-displayed peptide libraries on the human LDLR (hLDLR) stably expressed in cell lines led to the characterization of a family of cyclic and linear peptides that specifically bind the hLDLR. The VH411 lead cyclic peptide allowed endocytosis of payloads such as the S-Tag peptide or antibodies into cells expressing the hLDLR. Size reduction and chemical optimization of this lead peptide-vector led to improved receptor affinity. The optimized peptide-vectors were successfully conjugated to cargos of different nature and size including small organic molecules, siRNAs, peptides or a protein moiety such as an Fc fragment. We show that in all cases, the peptide-vectors retain their binding affinity to the hLDLR and potential for endocytosis. Following i.v. administration in wild type or ldlr-/- mice, an Fc fragment chemically conjugated or fused in C-terminal to peptide-vectors showed significant biodistribution in LDLR-enriched organs. We have thus developed highly versatile peptide-vectors endowed with good affinity for the LDLR as a target receptor. These peptide-vectors have the potential to be further developed for efficient transport of therapeutic or imaging agents into cells -including pathological cells—or organs that express the LDLR.

Efforts were made to improve a series of potent dual ABL/SRC inhibitors based on a 7-azaindole core with the aim of developing compounds that demonstrate a wider activity on selected oncogenic kinases. Multi-targeted kinase inhibitors (MTKIs) were then derived, focusing on kinases involved in both angiogenesis and tumorigenesis processes. Antiproliferative activity studies using different cellular models led to the discovery of a lead candidate (6z) that combined both antiangiogenic and antitumoral effects. The activity of 6z was assessed against a panel of kinases and cell lines including solid cancers and leukemia cell models to explore its potential therapeutic applications. With its potency and selectivity for oncogenic kinases, 6z was revealed to be a focused MTKI that should have a bright future in fighting a wide range of cancers.

Despite clinical advances in diagnosis and treatment, pancreatic ductal adenocarcinoma (PDAC) remains the third leading cause of cancer death, and is still associated with poor prognosis and dismal survival rates. Identifying novel PDAC-targeted tools to tackle these unmet clinical needs is thus an urgent requirement. Here we use a peptide conjugate that specifically targets PDAC through low-density lipoprotein receptor (LDLR). We demonstrate by using near-infrared fluorescence imaging the potential of this conjugate to specifically detect and discriminate primary PDAC from healthy organs including pancreas and from benign mass-forming chronic pancreatitis, as well as detect metastatic pancreatic cancer cells in healthy liver. This work paves the way towards clinical applications in which safe LDLR-targeting peptide conjugate promotes tumor-specific delivery of imaging and/or therapeutic agents, thereby leading to substantial improvements of the PDAC patient’s outcome.

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